Is there a way to animate a camera along a curve at specific speed?
I'm not sure how you can do it with the standard tools, but I figured out a way using animation nodes that seems to work (someone might need to check my math). I basically created a subprogram that takes a Spline input and an object input(what will move along the spline). Then using some math, it takes the spline length, number of frames in the scene and a speed number and moves all the objects along their respective curves at that speed.

Maybe this will help you out, here's an example file.





edit: Thinking through this, you can probably replace the end frame value with just a float number set to some high number. That way this would keep the speed the same regardless of how long the scene is.